Isn't it possible that the grappling hook footage scene was featured in a documentary or show of some kind? Not as an entire scene, but maybe as an out-take? That doesn't require a new IP.
I just find it hard to believe that all this is solely based on the novelization.
And this is aside the point, but didn't a small amount of the Biggs footage appear in a TV-aired SW documentary in the 80s?